"As is usual with cultivated plants they grow best in conditions that resemble those found in their natural habitat. ' Streptocarpus' by Rex Dibley
So what is the typical habitat of Streptocarpus in the wild? Streptocarpus originate from Africa with a few species possibly in Asia but there is doubt to their true affinities. They require rain in the summer and good drainage and partial shade. They are found growing on banks, alongside streams and on the surfaces of rocks and tree trunks. Knowing this we can assume that they prefer bright but not direct sunlight (dappled shade) cool temperatures and good humidity similar to the conditions found in high mountain woodlands.
Streps need bright light but not direct sun. They can easily be grown in east and west facing windows as well as under fluorescent lights. Some early morning or late evening sun shouldn't harm them but direct sun during the mid day can cause burning to the leaves and the flowers. It is important they get adequate light as to little light leads to plants producing very large leaves and little or no blooms. The book 'The Miracle Houseplants' states 750 foot candles is ample. You can also successfully grow your plants under a two tube 'shop light' fixture with a cool and warm bulb or full spectrum fluorescent lights with about 12-14 hours of light per day and get nice results.
Streptocarpus prefer to be grown in cool conditions. Growing temperatures should remain between 55 and 75 if possible. Like plants that are grown outside I think it is very important that we keep the roots as cool as possible to keep our plants happy.
Streptocarpus have fairly shallow root systems and seem to prefer and grow much better in the "pan" or "azalea" style pots. This is because they have a shallow root system. Dibley's states that they prefer plastic to clay pots as the roots will fix themselves into the pores of the clay and are then very difficult (if not impossible) to remove. It is also encouraged to keep the plants on the root bound or pot bound side. They become more floriferous this way. If properly cared for and feed they will flourish. Remember they can live in very little soil on the surfaces of rocks. I do however believe it is important to re-pot with fresh soil at least once a year.
Dibley's Encourage a "good proprietary peat-based compost" for potting them in. The book 'The Miracle Houseplants' recommends a more "gritty" mix.
1 1/2 parts peat
1 part perlite
1 part vermiculite
2 parts granite or conglomerate gravel (particles no larger than 1/4 inch)
2 tablespoons lime chips to the quart.
Here is another good recipe.
1 part peat
1 part vermiculite
1 part perlite
I wick water and use a 25% peat to 75% perlite and feel this is a good mix for me. If wicking be sure to add a lot of perlite to 'lighten' up the mix and help avoid root rot.
It is also stated in 'The Miracle Houseplants' that streps like alkaline soil. This is the only time I have ever read or heard of this. In fact I haven't seen any other information on the preferred pH other than that.
This seems to be where most people go wrong and loose their plants. Streps hate having soggy feet. You need to learn to judge when your plant needs to be watered. One of the easiest ways is to pick up the pot and judge by the weight of it. Don't water unless the pot feels considerably lighter than right after you water it. You can also use your fingers to check the moistness of the soil. If the first 1/2 inch is dry it might need some more water. Some also prefer to wait for the first signs of wilt before watering. If wick watering the plant soil will be constantly moist so be sure to use a very light potting mix. If the soil holds to much moisture your plant will get root rot.
Plants should be feed with a fertilizer high in potash. This is the third number you will find on the package. They are listed as nitrogen, phosphorus and potassium content. What are these and what do they do you say?
N = Nitrogen 7-9-5 Nitrogen is the first major element responsible for the vegetative growth of plants above ground. With a good supply, plants grow sturdily and mature rapidly, with rich, dark green foliage.
P = Phosphorus 7-9-5 The second major element in plant nutrition, phosphorus is essential for healthy growth, strong roots, fruit and flower development, and greater resistance to disease.
K = Potassium (Potash) 7-9-5 The third major plant nutrient, potassium oxide is essential for the development of strong plants. It helps plants to resist diseases, protects them from the cold and protects during dry weather by preventing excessive water loss.
It is also important to have the necessary micronutrients. Plants don't live on nitrogen, phosphorus, and potassium alone. They also need other nutrients, including calcium, magnesium, and sulfur to name a few to grow healthy.
Many growers feed their plants a constant feed at 1/4 the recommended strength fertilizer or fertilize once a month with the recommended strength.
I would also like to stress the importance of leaching your plants monthly. Flush clear water through your plants so that it drains out the bottom until the water washes through clear. This helps prevent damage to your plants from the salt buildup fertilizers can leaves behind.
'Streptocarpus' by Rex Dibley
'The Miracle Houseplants' by Virginie F. and George A. Elbert